Certain computing systems allow the creation of workflows including sequences of operations configured such that the output created by a previous operation is input to the next operation. For example, on many Unix-style operating systems, such sequences are provided by connecting operations (e.g., shell commands) using operators such as “|”, “<”, and “>.” A sequence such as “ps|grep ‘blah’” will cause the output of the command “ps” to be provided to the program “grep” as a stream such that the two commands run in parallel.